Ask Hackaday: Auto Bed Leveling And High Temperature Force Sensitive Resistors

FSR

[Johann] over on the RepRap wiki has an ingenious solution for making sure a borosilicate glass bed is completely level before printing anything on his Kossel printer: take three force sensitive resistors, put them under the build platform, and wire them in parallel, and connect them to a thermistor input on an electronics board. The calibration is simply a bit of code in the Marlin firmware that touches the nozzle to the bed until the thermistor input maxes out. When it does, the firmware knows the print head has zeroed out and can calculate the precise position and tilt of the bed.

Great, huh? A solution to bed leveling that doesn’t require a Z-probe, uses minimal (and cheap) hardware, and can be retrofitted into just about any existing printer. There’s a problem, though: these force sensitive resistors are only good to 70° C, making the whole setup unusable for anything with a heated bed. Your challenge: figure out a way to use this trick with a heated bed.

The force sensitive resistors used – here’s a link provided by [Johann] – have a maximum operating temperature of 70° C, while the bed temperature when printing with ABS is around 130° C. The FSRs are sensitive to temperature, as well, making this a very interesting problem.

Anyone with any ideas is welcome to comment here, on the RepRap forums, the IRC, or anywhere else. One idea includes putting an FSR in the x carriage, but we’re thinking some sort of specialized heat sink underneath the bed and on top of the FSRs would be a better solution.

Video of the auto bed leveling trick in action below.

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Ask Hackaday: Wiping Your Bum With An Arduino?

TP

Over or under? Standing or sitting? Truly, toilet paper has been the focus of the most irreconcilable arguments ever. The folks on the Arduino Stack Exchange have a far more important question: how do you trigger an alarm when your TP supply is low?

[user706837] asked the Internet this question in response to his kids never replacing an empty roll. This eliminates the most obvious means of notifying someone of an empty roll – looking at it before you sit down – and brings up a few interesting engineering challenges.

Most of the initial ideas deal with weight or some sort of light sensor that can differentiate between the white TP and the brown roll. A much, much more interesting solution puts a radioactive source in the TP holder’s spring-loaded rod and uses a sensor to detect how much TP is left. A quick back-of-the-wolfram calculation suggests this might be possible, and amazingly, not too dangerous.

We’re turning this one over to you, Hackaday readers. How would you design an empty toilet paper alarm? Bonus points awarded for ingenuity and cat resistance.

Image source, and also one of the longest and most absurd Wikipedia articles ever.

Ask Hackaday: What’s Up With This Carbon Fiber Printer?

mark

The Hackaday Tip Line has been ringing with submissions about the Mark Forg3D printer, purportedly the, “world’s first 3D printer that can print carbon fiber.”

Right off the bat, we’re going to call that claim a baldfaced lie. Here’s a Kickstarter from a few months ago that put carbon fiber in PLA filament, making every desktop 3D printer one that can print in carbon fiber.

But perhaps there’s something more here. The Mark Forged site gives little in the way of technical details, but from what we can gather from their promo video, here’s what we have: it’s a very impressive-looking aluminum chassis with a build area of 12″x6.25″x6.25″. There are dual extruders, with (I think) one dedicated to PLA and Nylon, and another to the carbon and fiberglass filaments. Layer height is 0.1mm for the PLA and Nylon, 0.2mm for the composites. Connectivity is through Wifi, USB, or an SD card, with a “cloud based” control interface. Here are the full specs, but you’re not going to get much more than the previous few sentences.

Oh, wait, it’s going to be priced at around $5000, which is, “affordable enough for average consumers to afford.” Try to contain your laughter as you click the ‘read more’ link.

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Ask Hackaday: (How) should we control Kickstarter campaigns?

Kickstarter campaigns helped bring new and innovative products to the market during these last years. However there often are failures that can happen at several stages. We’d like to hear your opinion about them and discover what you think could be done to foresee/prevent these kinds of bad experiences that damage the trust between individuals and funding platforms.

Post-funding failures

There are a few project teams that give up a few months after receiving the funds, like the people behind the iControlPad 2 recently (disclaimer: we’re not backers). Even if [Craig] stated that he would document the entire production process on film and be open about all the project life steps, that didn’t prevent the project from being dropped (oddly enough) exactly one year after they received the funds. The more the project was headed towards failure, less was the frequency of updates regarding the project’s current state. The official reasons for this decision were difficulties that arose with the chosen LEDs, we’ll let you make your own opinion by having a look at the updates section. Thanks [Nikropht] for the tipping us about it.

Pre-funding failures

What is happening even more often on kickstarter is (usually successful) campaigns being canceled by the website itself after a few people rang the alarm bell. This may be due to an unfeasible project idea, a fake demonstration video/photos or even an attempt to resell an existing item under a new name.

The best examples for the first category undeniably are free energy generators. Here is an indiegogo campaign which actually succeeded. The creators announced one month ago that the project is running a bit behind schedule (aha), that the machine will cost around $5000 and that they’ll “need the funds before they make the units”. What can be done to educate the public that such energy is not created out of thin air?

The second category includes the recently canceled LUCI advanced lucid dream inducer (thanks [Michael] for the tip), which ended 2 days before the deadline. Technical guys got skeptical when they saw that the electrode signals were amplified several feet from the brain with an audio amplifier. At first glance, this was the only sign that this project may have been a scam (let’s give them the benefit of the doubt). Further research indicated that GXP (the company behind the campaign) didn’t exist, and most of their pictures were photoshopped. Here is a link to a quick summary of the situation and if you want to be entertained we advise you to make some pop-corn and head to the comments section of the project. What’s terrible here is that backers started to turn against each other, as the company always had a ‘good’ explanation for all the backers’ questions.

At last, there are some persons that just make funding campaigns with already existing products. This is the case of the eye3 flying robot and the vybe vibrating bracelet (don’t order!). Note that all of them were successfully funded. The eye3 was created by the same persons that made LumenLab, a company that created the microcnc. You’ll find more details here. The vibrating bracelet was just this one, which would be made in different colors. We just discovered this website that covered both project in greater lengths as well as many others.

Kickstarter fraudsters

Scams can also happen on the backers’ side. Recently, a Kickstarter backer named “Encik Farhan” attempted to rip off many Kickstarter projects. A ‘credit card chargeback’ technique was used, were the backer would contribute to the campaign, receive his perk and later cancel his credit card transaction using diverse reasons. The money would later be taken from the campaign funding by the payment processor.

What can be done?

The examples cited in this article set precedents which may turn people away from crowdfunding. In your opinion, what could be done to prevent this? Another reason we ask is because Hackaday may launch a sponsored product soon, thanks to the new overlords. This hypothetical product would be designed with the Hackaday community in a completely transparent process.

In the meantime, if you find any perpetual motion machines on kicstarter or indiegogo, be sure to send them in. You may also want to checkout this website predicting the success probability of a given kickstarter campaign.

Ask Hackaday: Can you Hack an Appliance into a Spy Device?

crackinGoodTeapot

A story surfaced a few days before Halloween on Russian news site Rosbalt (yep, that’s in Russian), claiming Russian authorities intercepted Chinese-made electric irons and kettles: each equipped with microphones and WiFi. You can read a summary in English on the BBC’s website. The “threat” imposed by these “spy appliances” is likely the result of gross exaggeration if not downright fear mongering against Chinese-made products. It’s not worth our (or your) effort to speculate on what’s really happening here, but the situation does present a fun exercise.

Say you wanted to spice up your pen testing by altering a small home appliance: how easily could you build it? Let us know in the comments which appliance would serve as the best “host” for the modifications and what features you would include. Could you manage all the components listed in the article–a microphone, WiFi (any chance of cracking unsecured networks?), plus some vague indication that it “spreads viruses?” There’s a video below with a few glimpses of the electronics in question, but unless you speak Russian it probably won’t offer much insight.

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Ask Hackaday: Does Project Ara Solve the Phonebloks’ Problems?

motorolaProjectAra

Our tips line is blowing up again, this time directing us to Motorola’s Project Ara: a phone with modular components that plug into a base “endoskeleton.” If you missed the news coverage strewn across the web and you are doing a double-take, that’s because Project Ara is frighteningly similar to the (presumed vaporware) Phonebloks concept from a few weeks ago. Phonebloks was the subject of our last “Ask Hackaday” article, generating hundreds of comments ranging from those defending the concept to those furiously opposed to it.

There’s a conspiracy theory circulating that suggests Motorola released the Phonebloks concept as a viral marketing scheme to generate hype before revealing the official product line. We suspect it’s a bit less conniving. As [jorde] explained on Hacker News, an Israeli startup, Modu, had developed a similar modular cell phone several years ago, and Google bought the patents in May of 2011. A few months later, Google bought something else: Motorola. It seems likely that Project Ara is merely a resurrected and revised Modu, and Motorola conveniently announced it in the wake of Phonebloks’ popularity. Regardless, Motorola has announced that they have partnered with Phonebloks’ creator Dave Hakkens .

So what’s different? Phonebloks was met with cries of “vaporware!” and fervent arguments raising concerns about unavoidable hardware limitations. Motorola claims their goal is:

to do for hardware what the Android platform has done for software: create a vibrant third-party developer ecosystem, lower the barriers to entry, increase the pace of innovation, and substantially compress development timelines.

Unlike Project Ara, Phonebloks didn’t consider open-source hardware (Wayback Machine link), and Motorola makes an interesting argument here: that advances in 3D printing indicate an evolving “open hardware ecosystem,” and the next era of phone development may rest in the hands of your average hacker or a small startup company. Some speculate that the Ara will be similar to the relationship between a PC and its peripherals: Motorola provides the essential guts while giving you some slots for attaching additional components. Let us know in the comments what you think about Project Ara: is it just more vaporware, or a watered-down but plausible alternative to Phonebloks?  And, perhaps most important: do you, as a hacker, want a phone that supports open hardware and lets you plug in “peripherals?” The Phonebloks website has since changed to reflect the partnership with Motorola, and includes a new video that you can watch below.

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How Do You Build a Relay CPU?

relay

The Hackaday tips line is always full of the coolest completed projects, but only rarely do we see people reaching out for help on their latest build. We’ll help when we can, but [Tim]‘s relay-based CPU has us stumped.

[Tim] already has the design of his relay CPU completed with a 12-bit program counter, sequencer, ALU, and a transistor-based ROM. The problem he’s having deals with the mechanics and layout of his homebuilt CPU. Right now, all the relays (PC pin, we guess) are glued top-down to a piece of cardboard. This allows him to easily solder the wires up and change out the inevitable mistakes. This comes with a drawback, though: he’s dealing with a lot of ‘cable salad’ and it’s not exactly the prettiest project ever.

The ideal solution, [Tim] says, would be a PCB with through-hole plating, but this isn’t easy or cheap for the home fab lab. We’d suggest some sort of wire wrap setup, but proper wire wrap sockets and protoboards are for some reason unreasonably expensive.

If you have an idea on how to do the mechanical layout and connections of a relay-based computer, drop a note in the comments. [Tim] has a very cool project here, and it would be a shame if he were to give up on it due to a lack of tools.

Video below, and if you’re having a problem with a project, feel free to send it in.

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